An experimental study about R134a refrigerant flow boiling in a horizontal multiport flat tube mini-channel with the hydraulic diameter of 0.63mm and 0.72mm was carried out. The refrigerant was heated in uniform heat flux. The experiments were performed at the mass flux in range of 82-621kg/(m2·s)

heat flux in range of 9.7-64kW/m2

saturation pressure in range of 0.22-0.63MPa and vapor quality in range of 0-1. Results showed that when the vapor quality in range of 0-0.6

the local heat transfer coefficients of mini-channel were higher than those of conventional channel

nucleate boiling was the main contributing factor

the local heat transfer coefficients increased with increasing heat flux and saturation pressure

but had little dependence with mass flux. When the vapor quality was bigger than 0.6

the local transfer coefficients decreased sharply; the influences of heat flux and saturation pressure on local heat transfer coefficient were small

but closely related to mass flux. Gungor-Winterton correlation was modified based on the experimental R134a flow boiling heat transfer coefficient from present study and published literatures

with -1.71% of the mean relation deviation and 19.24% of the mean absolute relation deviation respectively

showing an obvious improvement.